Method for producing silicon carbide powder, silicon carbide powder and application thereof

Abstract

The present invention relates to the technical field of silicon carbide preparation, and discloses a method for producing silicon carbide powder, silicon carbide powder and its application. The method comprises: subjecting a raw material to a first synthesis reaction; subjecting the product of the first synthesis reaction to a second synthesis reaction in the presence of an inert gas; wherein the raw material is obtained by stacking a mixture A and a mixture B in a vertical direction, and both the mixture A and the mixture B contain silicon powder and carbon powder; the number of layers of the mixture A is the same as the number of layers of the mixture B and is not less than 1; the silicon-carbon molar ratio of the mixture A is greater than 1:1; the silicon-carbon molar ratio of the mixture B is less than 1:1; the amount of the mixture A and the mixture B makes the silicon-carbon molar ratio of the raw material equal to 1:1-1.03. The method can avoid the upper and lower stratification of silicon and carbon in the early stage of the reaction, so that the mixture reacts and mixes again between layers during the reaction process, achieving a more sufficient reaction, thereby improving the yield. In addition, the method does not introduce new impurities and has low cost.

Description

Technical Field

[0001] The invention relates to the technical field of silicon carbide preparation, and in particular to a method for producing silicon carbide powder, the silicon carbide powder and applications thereof. Background Art

[0002] The development and progress of semiconductor devices is one of the main driving forces for promoting equipment upgrades and technological innovation. As one of the important representatives of the third-generation semiconductor materials, silicon carbide has become a popular material for the preparation of semiconductor devices due to its excellent properties such as large bandgap, high saturated electron mobility, strong breakdown field, and high thermal conductivity. Impurities in silicon carbide substrates are one of the key factors restricting the performance of silicon carbide semiconductor devices. Therefore, the preparation of high-purity silicon carbide powder has become a core technology for controlling impurities in silicon carbide substrates.

[0003] At present, the preparation of silicon carbide powder is mainly achieved by high-temperature self-propagating synthesis, which obtains silicon carbide powder by direct contact and reaction between carbon powder and silicon powder. In order to obtain high-purity silicon carbide powder, the high-temperature self-propagating synthesis method has been continuously optimized and relatively high-purity silicon carbide powder has been obtained.

[0004] The most commonly used method for synthesizing silicon carbide powder in production at present is the self-propagating high-temperature synthesis method, which is to heat high-purity carbon powder and silicon powder to above 2000°C in a medium-frequency electromagnetic induction furnace and synthesize silicon carbide powder in an argon and / or helium atmosphere.

[0005] CN101302011A discloses a method for artificially synthesizing high-purity silicon carbide powder for growing semiconductor single crystals. The method adopts a two-step synthesis method. First, Si powder and C powder with a molar ratio of 1:1 are mixed evenly, and then the temperature is increased from 1000°C to 1500°C in a medium-frequency electromagnetic induction furnace. The mixture is reacted in an atmosphere of high-purity argon, helium or a mixed gas of argon and hydrogen. Then, the resulting product powder is further synthesized at 1600°C to 2000°C in an atmosphere of high-purity argon, hydrogen or a mixed gas of the two to prepare high-purity SiC powder.

[0006] However, as the demand for silicon carbide substrate diameter increases, the amount of silicon carbide powder required for a single ingot growth furnace increases accordingly. In order to increase the output of silicon carbide powder, the diameter and height of the graphite crucible used to produce silicon carbide powder are increased, and the mass of the high-purity carbon powder and high-purity silicon powder mixture loaded at a time is increased. Since the particle sizes of high-purity carbon powder and high-purity silicon powder are not completely consistent, and the synthesis time of silicon carbide powder in a large crucible is often as long as 3 to 4 days, a certain degree of stratification will occur during the synthesis process, making it impossible to evenly mix the carbon powder and silicon powder, resulting in an incomplete reaction, thereby reducing the output of silicon carbide powder. Summary of the invention

[0007] The purpose of the present invention is to overcome the problem of insufficient reaction caused by stratification of silicon-carbon raw materials in the synthesis process of silicon carbide powder in the prior art, and to provide a method for producing silicon carbide powder, silicon carbide powder and its application to improve the effective yield of silicon carbide powder under large mass (large size).

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for producing silicon carbide powder, the method comprising the following steps:

[0009] (1) subjecting the raw materials to a first synthesis reaction; wherein the conditions of the first synthesis reaction include: a vacuum degree of 5-90 kPa; a temperature of 1200-1600° C.;

[0010] The raw material is obtained by stacking a mixture A and a mixture B in a vertical direction, and both the mixture A and the mixture B contain silicon powder and carbon powder; the number of layers of the mixture A is the same as the number of layers of the mixture B, and the number of layers is not less than 1; the silicon-carbon molar ratio of the mixture A is greater than 1:1; the silicon-carbon molar ratio of the mixture B is less than 1:1; and the amount of the mixture A and the mixture B is such that the silicon-carbon molar ratio of the raw material is equal to 1:1-1.03;

[0011] (2) In the presence of an inert gas, subjecting the product of the first synthesis reaction to a second synthesis reaction to obtain silicon carbide powder; wherein the conditions of the second synthesis reaction include: a pressure of 40-90 kPa; and a temperature of 1800-2400°C.

[0012] The second aspect of the present invention provides a silicon carbide powder prepared by the method described in the first aspect, wherein the silicon carbide powder comprises high-purity α silicon carbide powder and high-purity β silicon carbide powder.

[0013] The third aspect of the present invention provides use of the silicon carbide powder described in the second aspect in preparing a semiconductor device.

[0014] Through the above technical solution, the method provided by the present invention can avoid the upper and lower stratification of silicon and carbon in the early stage of the reaction through a special loading method, and can make the mixed material react and mix again between layers during the reaction process, so as to achieve a more complete reaction and thus improve the yield. In addition, the method provided by the present invention does not introduce new impurities and has low cost. DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] In the present invention, the particle sizes of the carbon powder and the silicon powder are uniform or non-uniform.

[0017] A first aspect of the present invention provides a method for producing silicon carbide powder, the method comprising the following steps:

[0018] (1) subjecting the raw materials to a first synthesis reaction; wherein the conditions of the first synthesis reaction include: a vacuum degree of 5-90 kPa; a temperature of 1200-1600° C.;

[0019] The raw material is obtained by stacking a mixture A and a mixture B in a vertical direction, and both the mixture A and the mixture B contain silicon powder and carbon powder; the number of layers of the mixture A is the same as the number of layers of the mixture B, and the number of layers is not less than 1; the silicon-carbon molar ratio of the mixture A is greater than 1:1; the silicon-carbon molar ratio of the mixture B is less than 1:1; and the amount of the mixture A and the mixture B is such that the silicon-carbon molar ratio of the raw material is equal to 1:1-1.03;

[0020] (2) In the presence of an inert gas, subjecting the product of the first synthesis reaction to a second synthesis reaction to obtain silicon carbide powder; wherein the conditions of the second synthesis reaction include: a pressure of 40-90 kPa; and a temperature of 1800-2400°C.

[0021] In the prior art, in order to increase the output of silicon carbide powder, the diameter and height of the graphite crucible used to produce silicon carbide powder are increased, and the mass of the mixture formed by the single loading of high-purity carbon powder and high-purity silicon powder is increased. Since the particle sizes of high-purity carbon powder and high-purity silicon powder are not completely consistent, and the synthesis time of silicon carbide powder with large mass (large size) is long, the mixture is easy to stratify, which reduces the uniformity of carbon powder and silicon powder, resulting in incomplete reaction, and reduces the output of silicon carbide powder.

[0022] The method provided by the present invention uses a special loading method to stack the mixture A and the mixture B with a specific silicon-carbon molar ratio in sequence in the vertical direction, and subject the obtained raw materials to a first synthesis reaction and a second synthesis reaction under specific conditions to produce silicon carbide powder. This not only avoids the upper and lower stratification of silicon and carbon in the early stage of the reaction, but also allows the mixture to react and mix again between layers during the reaction to achieve a more sufficient reaction, thereby increasing the yield of silicon carbide powder, especially increasing the yield of silicon carbide powder under large mass (large size), but also does not introduce new impurities and has a low cost.

[0023] According to some embodiments of the present invention, in step (1), the raw material is obtained by stacking a mixture A and a mixture B in a vertical direction. Preferably, the stacking method includes: covering the mixture A at the bottom of the reaction container, then laminating, then covering the mixture B and then laminating, and repeating the above process; or, covering the mixture B at the bottom of the reaction container, then laminating, then covering the mixture A and then laminating, and repeating the above process. The use of the above preferred embodiment is conducive to further promoting the reaction between the silicon powder and the carbon powder in the raw material, thereby further improving the yield of silicon carbide powder, especially improving the yield of silicon carbide powder under large mass (large size), and can improve the purity of silicon carbide powder.

[0024] According to some embodiments of the present invention, the number of layers of the mixture A is the same as the number of layers of the mixture B, and the number of layers is not less than 1. In order to further improve the yield of the silicon carbide powder, preferably, the number of layers of the mixture A and the number of layers of the mixture B are 10-100. The number of layers of the mixture A and the number of layers of the mixture B can be determined according to the volume of the charge.

[0025] According to some embodiments of the present invention, in step (1), both the mixture A and the mixture B contain silicon powder and carbon powder. Preferably, the mixture A and the mixture B are obtained by mixing silicon powder and carbon powder respectively, and the mixing time is not less than 0.5h, preferably 0.5-25h. The above preferred embodiment is conducive to the full mixing of silicon powder and carbon powder, and the reaction is more uniform and sufficient.

[0026] According to some embodiments of the present invention, the silicon-carbon molar ratio of the mixture A is greater than 1:1; preferably, the silicon-carbon molar ratio of the mixture A is 1:0.9-0.98.

[0027] According to some embodiments of the present invention, the silicon-carbon molar ratio of the mixture B is less than 1:1; preferably, the silicon-carbon molar ratio of the mixture B is 1:1.05-1.1.

[0028] The use of the above preferred embodiment is beneficial to further promote the reaction between the silicon powder and the carbon powder in the raw material, thereby further improving the yield of silicon carbide powder, especially improving the yield of silicon carbide powder under large mass (large size), and can improve the purity of silicon carbide powder.

[0029] According to some embodiments of the present invention, preferably, in step (1), the thickness of the AB unit formed by any of the mixtures A and the adjacent mixtures B is the same.

[0030] According to some embodiments of the present invention, preferably, the thickness of the AB unit is 0.1-1 cm.

[0031] In the present invention, the thickness of the AB unit meets the above conditions, which is beneficial to further promote the full reaction of the raw materials and improve the reaction effect while ensuring low cost.

[0032] According to some embodiments of the present invention, preferably, in step (1), the maximum particle size of the silicon powder is not greater than 100 μm, preferably not greater than 80 μm; and the purity of the silicon powder is not less than 99%, preferably not less than 99.99%.

[0033] According to some embodiments of the present invention, preferably, the maximum particle size of the carbon powder is not greater than 100 μm, preferably not greater than 80 μm; the purity of the carbon powder is not less than 99%, preferably not less than 99.99%.

[0034] According to some embodiments of the present invention, preferably, in step (1), the time of the first synthesis reaction is not less than 2 hours, preferably 2-15 hours.

[0035] According to some embodiments of the present invention, in step (1), the raw materials are subjected to a first synthesis reaction, and the product of the first synthesis reaction contains high-purity β-silicon carbide powder.

[0036] According to some embodiments of the present invention, preferably, in step (2), the time of the second synthesis reaction is not less than 10 h, preferably 10-40 h.

[0037] According to some embodiments of the present invention, in step (2), the product of the first synthesis reaction is subjected to a second synthesis reaction in the presence of an inert gas to obtain silicon carbide powder. Preferably, the inert gas is argon and / or helium.

[0038] According to a particularly preferred embodiment of the present invention, the method for producing silicon carbide powder comprises the following steps:

[0039] (S1) Covering the bottom of the reaction container with mixed material A, then laminating, then covering with mixed material B, then laminating, and repeating the above process; or, covering the bottom of the reaction container with the mixed material B, then laminating, then covering with the mixed material A, then laminating, and repeating the above process; obtaining a raw material in which mixed material A and mixed material B are stacked in sequence in a vertical direction;

[0040] Wherein, the mixture A and the mixture B are obtained by mixing silicon powder and carbon powder respectively, and the mixing time is 0.5-25h; the silicon-carbon molar ratio of the mixture A is 1:0.9-0.98; the silicon-carbon molar ratio of the mixture B is 1:1.05-1.1; the number of layers of the mixture A is the same as the number of layers of the mixture B, and the number of layers is 10-100; the amount of the mixture A and the mixture B is such that the silicon-carbon molar ratio of the raw materials is equal to 1:1-1.03; the thickness of the AB unit formed by any of the mixtures A and the adjacent mixture B is the same, and the thickness of the AB unit is 0.1-1cm; the maximum particle size of the silicon powder is not greater than 100μm, and the purity is not less than 99.99%; the maximum particle size of the carbon powder is not greater than 100μm, and the purity is not less than 99.99%;

[0041] (S2) subjecting the raw materials to a first synthesis reaction; wherein the conditions of the first synthesis reaction include: a vacuum degree of 5-90 kPa; a temperature of 1200-1600° C.; and a time of 2-15 h;

[0042] (S3) In the presence of an inert gas, subjecting the product of the first synthesis reaction to a second synthesis reaction to obtain silicon carbide powder; wherein the conditions of the second synthesis reaction include: a pressure of 40-90 kPa; a temperature of 1800-2400° C.; and a time of 10-40 h.

[0043] The second aspect of the present invention provides a silicon carbide powder prepared by the method described in the first aspect, wherein the silicon carbide powder comprises high-purity α silicon carbide powder and high-purity β silicon carbide powder.

[0044] According to some embodiments of the present invention, preferably, in the silicon carbide powder, the mass ratio of high-purity α silicon carbide powder to high-purity β silicon carbide powder is 9-50:1.

[0045] The third aspect of the present invention provides use of the silicon carbide powder described in the second aspect in preparing a semiconductor device.

[0046] The present invention will be described in detail below through examples.

[0047] In the following examples and comparative examples, unless otherwise specified, the raw materials used are commercially available products.

[0048] The silicon powder is high-purity silicon powder purchased from Wacker Company / Manufacturer in Germany, with a particle size of 0.02-0.1 mm and a purity of 99.999%;

[0049] The carbon powder is high-purity carbon powder purchased from SGL Corporation / manufacturer in Germany, with a particle size of 0.02-0.1 mm and a purity of 99.9999%.

[0050] Example 1

[0051] (1) mixing silicon powder and carbon powder in a mixer to obtain a mixture A; wherein the mixing time is 0.5 h; and the amounts of silicon powder and carbon powder are such that the silicon-carbon molar ratio of the mixture A is 1:0.95;

[0052] (2) mixing silicon powder and carbon powder in a mixer to obtain a mixture B; wherein the mixing time is 0.5 h; and the amount of silicon powder and carbon powder is such that the silicon-carbon molar ratio of the mixture B is 1:1.05;

[0053] (3) Covering the bottom of the graphite crucible with mixed material A, and then laminating, and then covering with mixed material B and laminating, repeating the above process to obtain a raw material obtained by stacking mixed material A and mixed material B in sequence in a vertical direction, the number of layers of mixed material A is the same as the number of layers of mixed material B, and the number of layers is 100, and the amount of mixed material A and mixed material B is such that the silicon-carbon molar ratio of the raw material is equal to 1:1; the thickness of the AB unit formed by any mixed material A and the adjacent mixed material B is the same, and the thickness of the AB unit is 0.5 cm;

[0054] (4) subjecting the raw materials to a first synthesis reaction; wherein the conditions of the first synthesis reaction include: a vacuum degree of 10 kPa; a temperature of 1600° C.; and a time of 2 h;

[0055] (5) In the presence of argon, subjecting the product of the first synthesis reaction to a second synthesis reaction to obtain silicon carbide powder; wherein the conditions of the second synthesis reaction include: a pressure of 40 kPa; a temperature of 2300° C.; and a time of 12 h; in the silicon carbide powder, the mass ratio of high-purity α silicon carbide powder to high-purity β silicon carbide powder is 95:5.

[0056] Example 2

[0057] (1) mixing silicon powder and carbon powder in a mixer to obtain a mixture A; wherein the mixing time is 1 hour; and the amounts of silicon powder and carbon powder are such that the silicon-carbon molar ratio of the mixture A is 1:0.95;

[0058] (2) mixing silicon powder and carbon powder in a mixer to obtain a mixture B; wherein the mixing time is 1 hour; and the amount of silicon powder and carbon powder is such that the silicon-carbon molar ratio of the mixture B is 1:1.05;

[0059] (3) Covering the bottom of the graphite crucible with mixed material A, and then laminating, and then covering with mixed material B and laminating, repeating the above process to obtain a raw material obtained by stacking mixed material A and mixed material B in sequence in a vertical direction, the number of layers of mixed material A is the same as the number of layers of mixed material B, and the number of layers is 100, and the amount of mixed material A and mixed material B is such that the silicon-carbon molar ratio of the raw material is equal to 1:1; the thickness of the AB unit formed by any mixed material A and the adjacent mixed material B is the same, and the thickness of the AB unit is 0.4 cm;

[0060] (4) subjecting the raw materials to a first synthesis reaction; wherein the conditions of the first synthesis reaction include: a vacuum degree of 10 kPa; a temperature of 1600° C.; and a time of 2 h;

[0061] (5) In the presence of argon, subjecting the product of the first synthesis reaction to a second synthesis reaction to obtain silicon carbide powder; wherein the conditions of the second synthesis reaction include: a pressure of 40 kPa; a temperature of 2300° C.; and a time of 12 h; in the silicon carbide powder, the mass ratio of high-purity α silicon carbide powder to high-purity β silicon carbide powder is 95:5.

[0062] Example 3

[0063] According to the method of Example 1, except that in step (1), the mixing time is 3 hours, and the rest is the same as Example 1, to obtain silicon carbide powder. In the silicon carbide powder, the mass ratio of high-purity α silicon carbide powder to high-purity β silicon carbide powder is 98:2.

[0064] Example 4

[0065] According to the method of Example 1, except that in step (1), the amount of silicon powder and carbon powder is such that the silicon-carbon molar ratio of the mixed material A is 1:0.9, and the rest is the same as in Example 1, to obtain silicon carbide powder. In the silicon carbide powder, the mass ratio of high-purity α silicon carbide powder to high-purity β silicon carbide powder is 90:10.

[0066] Example 5

[0067] According to the method of Example 1, except that in step (3), the thickness of the AB unit is 0.2 cm, and the rest is the same as Example 1, to obtain silicon carbide powder. In the silicon carbide powder, the mass ratio of high-purity α silicon carbide powder to high-purity β silicon carbide powder is 98:2.

[0068] Comparative Example 1

[0069] According to the method of Example 1, the difference is that silicon powder and carbon powder are mixed in a mixer to obtain a raw material; the amount of silicon powder and carbon powder is the same as the total amount of silicon powder and carbon powder in Example 1, and the silicon-carbon molar ratio of the raw material is equal to 1:1, and the rest is the same as Example 1 to obtain silicon carbide powder. In the silicon carbide powder, the mass ratio of high-purity α silicon carbide powder to high-purity β silicon carbide powder is 90:10.

[0070] The yields of the silicon carbide powder prepared in the embodiment and the comparative example were calculated respectively, and the results are shown in Table 1.

[0071] The yield of silicon carbide powder = mass of silicon carbide powder / mass of raw material × 100%.

[0072] Table 1

[0073]

[0074]

[0075] It can be seen from the results in Table 1 that the yield of silicon carbide powder produced by the method provided by the present invention can reach 63-77%, and the prepared silicon carbide powder has uniform color distribution, and there is no other black material except that part of the powder near the crucible wall is carbonized.

[0076] The yield of silicon carbide powder prepared in Comparative Example 1 is only 52%, which is much lower than that in Example 1. In addition, in addition to carbonization of part of the silicon carbide powder near the crucible wall, there are also unevenly distributed black materials and gray materials. These black materials and gray materials reduce the yield of silicon carbide powder and reduce the product quality.

[0077] In summary, the method provided by the present invention can avoid the upper and lower stratification of silicon and carbon in the early stage of the reaction, and can make the mixture react and mix again between layers during the reaction process, so as to achieve a more sufficient reaction and thus improve the yield.

[0078] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for producing silicon carbide powder, characterized in that: The method comprises the following steps: (1) subjecting the raw materials to a first synthesis reaction; wherein the conditions of the first synthesis reaction include: a vacuum degree of 5-90 kPa; a temperature of 1200-1600° C.; The raw material is obtained by stacking a mixture A and a mixture B in a vertical direction, and both the mixture A and the mixture B contain silicon powder and carbon powder; the number of layers of the mixture A is the same as the number of layers of the mixture B, and the number of layers is not less than 1; the silicon-carbon molar ratio of the mixture A is greater than 1:1; the silicon-carbon molar ratio of the mixture B is less than 1:1; and the amount of the mixture A and the mixture B is such that the silicon-carbon molar ratio of the raw material is equal to 1:1-1.03; (2) In the presence of an inert gas, subjecting the product of the first synthesis reaction to a second synthesis reaction to obtain silicon carbide powder; wherein the conditions of the second synthesis reaction include: a pressure of 40-90 kPa; and a temperature of 1800-2400°C.

2. The method according to claim 1, characterized in that In step (1), the stacking method includes: covering the mixture A at the bottom of the reaction container, then laminating, then covering the mixture B, then laminating, and repeating the above process; or, The bottom of the reaction container is covered with the mixture B, and then laminated, and then covered with the mixture A and laminated, and the above process is repeated; And / or, the number of layers of the mixture A and the number of layers of the mixture B are 10-100.

3. The method according to claim 1, characterized in that In step (1), the mixture A and the mixture B are obtained by mixing silicon powder and carbon powder respectively, and the mixing time is not less than 0.5h.

4. The method according to claim 3, characterized in that The mixing time is 0.5-25h.

5. The method according to any one of claims 1 to 4, characterized in that: In step (1), the molar ratio of silicon to carbon in the mixture A is 1:0.9-0.98; And / or, the molar ratio of silicon to carbon in the mixture B is 1:1.05-1.

1.

6. The method according to any one of claims 1 to 4, characterized in that: In step (1), the thickness of the AB unit formed by any of the mixtures A and the adjacent mixture B is the same.

7. The method according to claim 6, characterized in that The thickness of the AB unit is 0.1-1 cm.

8. The method according to any one of claims 1 to 4, characterized in that: In step (1), the maximum particle size of the silicon powder is not greater than 100 μm; the purity of the silicon powder is not less than 99%; And / or, the maximum particle size of the carbon powder is not greater than 100 μm; the purity of the carbon powder is not less than 99%.

9. The method according to claim 8, characterized in that In step (1), the maximum particle size of the silicon powder is not greater than 80 μm; the purity of the silicon powder is not less than 99.99%; And / or, the maximum particle size of the carbon powder is not greater than 80 μm; the purity of the carbon powder is not less than 99.99%.

10. The method according to any one of claims 1 to 4, characterized in that: In step (1), the time of the first synthesis reaction is not less than 2 hours.

11. The method according to claim 10, characterized in that In step (1), the time of the first synthesis reaction is 2-15h.

12. The method according to any one of claims 1 to 4, characterized in that: In step (2), the second synthesis reaction time is not less than 10 hours; And / or, the inert gas is argon and / or helium.

13. The method according to claim 12, characterized in that In step (2), the second synthesis reaction time is 10-40h.

14. A silicon carbide powder prepared by the method according to any one of claims 1 to 13, characterized in that: The silicon carbide powder includes high-purity α silicon carbide powder and high-purity β silicon carbide powder.

15. Use of the silicon carbide powder according to claim 14 in the preparation of semiconductor devices.

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